Simulation of the precipitation of calcium phosphates,sulfates, and carbonates from aqueous solutions of complex composition

The isothermal evaporation of aqueous solutions containing calcium, magnesium, and sodium carbonates, phosphates, sulfates, and chlorides was studied by physiochemical simulation methods. The equilibrium composition of the Ca(HCO₃)₂-Mg(HCO)₂-H₃PO₄-H₂SO₄-NaCl-CO₂-H₂O system was calculated for T = 25°C, pCO₂ = 10^?1 ? 10³ Pa, pH 7.7–9.4, solution concentration factors of 1–10, H₂SO₄ concentrations of 10^?4?9 × 10^?4 mol/(kg H₂O), an H₃PO₄ concentration of 2 × 10^?5 mol/(kg H₂O), and a NaCl concentration of 10^?3 mol/(kg H₂O). Conditions were determined for calcium precipitation as calcite, dolomite, gypsum, and hydroxylapatite. The results of simulation were used in the development of commercial-scale methods for stabilizing cooling solutions in circulating water supply systems.     

Inhibiting VOPO4⋅x H2O Decomposition and Dissolution in Rechargeable Aqueous Zinc Batteries to Promote Voltage and Capacity Stabilities

VOPO₄?x H₂O has been proposed as a cathode for rechargeable aqueous zinc batteries. However, it undergoes significant voltage decay in conventional Zn(OTf)₂ electrolyte. Investigations show the decomposition of VOPO₄?x H₂O into VO_x in the electrolyte and voltage drops after losing the inductive effect from polyanions.PO₄^3? was thus added to shift the decomposition equilibrium. A high concentration of cheap, highly soluble ZnCl₂ salt in the electrolyte further prevents VOPO₄?x H₂O dissolution. The cathode shows stable capacity and voltage retentions in 13 m ZnCl₂/0.8 m H₃PO₄ aqueous electrolyte, in direct contrast to that in Zn(OTf)₂ where the decomposition product VO_x provides most electrochemical activity over cycling. Sequential H⁺ and Zn²⁺ intercalations into the structure are revealed, delivering a high capacity (170 mAh g^?1). This work shows the potential issue with polyanion cathodes in zinc batteries and proposes an effective solution using fundamental chemical principles.     

Theoretical study of the structure and unimolecular decomposition pathways of ethyloxonium, [CH3CH2OH2]+

Ab initio molecular orbital calculations with split-valence plus polarization basis sets and incorporating valence-electron correlation have been performed to determine the equilibrium structure of ethyloxonium ([CH₃CH₂OH₂]⁺) and examine its modes of unimolecular dissociation. An asymmetric structure (1) is predicted to be the most stable form of ethyloxonium, but a second conformational isomer of C_s symmetry lies only 1.4 kJ mol^?1 higher in energy than 1. Four unimolecular decomposition pathways for 1 have been examined involving loss of H₂, CH₄, H₂O or C₂H₄. The most stable fragmentation products, lying 65 kJ mol^?1 above 1, are associated with the H₂ elimination reaction. However, large barriers of 257 and 223 kJ mol^?1 have to be surmounted for H₂ and CH₄ loss, respectively. On the other hand, elimination of either C₂H₄ or H₂O from ethyloxonium can proceed without a barrier to the reverse associations and, with total endothermicities of 130 and 160 kJ mol^?1, respectively, these reactions are expected to dominate at lower energies. A second important equilibrium structure on the surface is a hydrogen-bridged complex, lying 53 kJ mol^?1 above 1. This complex is involved in the C₂H₄ elimination reaction, acts as an intermediate in the proton-transfer reaction connecting [C₂H₅]⁺ +H₂O and C₂H₄ + [H₃O]⁺ and plays an important role in the isotopic scrambling that has been observed experimentally in the elimination of either H₂O or C₂H₄ from ethyloxonium. The proton affinity of ethanol was calculated as 799 kJ mol^?1, in close agreement with the experimental value of 794 kJ mol^?1.     

Anion Recognition Using Novel and Colorimetric Tweezer Receptors:1,3-Phenylenedi(carbonylhydrazone) in Aqueous-organic Binary Solvents

本文设计合成了2种新型的间苯二甲酰腙类钳形受体。在DMSO和DMSO-H2O混合溶液中,通过紫外可见光谱分别考察了受体分子3a对F-, Cl-, Br-, I-, AcO-, HSO4-, H2PO4-和ClO4-的相互作用。结果表明,在DMSO溶液中,受体3a对F-,CH3COO-和H2PO4-有显著识别效果,溶液颜色由无色变为黄色,实现裸眼检测。在15%H2O-85%DMSO含水体系中,3a可高选择性识别CH3COO-。1H NMR滴定表明过量F-的加入使受体分子3a发生脱质子作用,探讨了主客体之间的作用机理。并直接用于水相中无机醋酸盐的直接显色检测。     

Phosphoryl transfer from phenyl and 4-nitrophenyl phosphates in aprotic and protic solvents : Amine catalysis and formation of oxyphosphorane and metaphosphate intermediates

The behavior of 4-nitrophenyl dihydrogen phosphate, ArOPO₃H₂, and of its tetra-n-butylammonium and tetramethylammonium salts, ArOPO₃H^?R₄N⁺, ArOPO₃^2?2(R₄N⁺), was studied in aprotic solvents, in the absence and in the presence of increasing amounts of alcohols or water. The reactions were investigated in the absence of amines, and in the presence of hindered and unhindered amines, diisopropylethylamine and quinuclidine. The course of the reactions was followed at 35° or at 70° by ³¹P and ¹H NMR spectrometry. Values for the approximate half-times of the reactions were estimated (± 25 %) from the times at which reactant signal intensity becomes equal to product signal intensity. The mononitrophenyl ester transfers its phosphoryl group to alcohols and water from the diprotonated acid by the addition-elimination mechanism via oxyphosphorane intermediates, and from the monoanion and dianion by the elimination-addition mechanism via the monomeric metaphosphate intermediate, PO₃^?. Formation of PO₃^? is faster from dianion than from monoanion in acetonitrile and in alcohol solutions. Conversely, PO₃^? is generated at a faster rate from monoanion than from dianion in aqueous solution. This effect results from a decrease in the rate of formation of PO₃^? in the solvent series: acetonitrile > alcohols > water. The rate depression as a function of the medium is greater for the dianion than for the monoanion, and is attributed to greater solvation of the more polar phosphate ground state than of the less polar transition state in the more polar protic solvents. Unhindered amines add to 4-nitrophenyl phosphate monoanion, but not to the dianion. The oxyphosphorane intermediate thus formed collapses to aroxide ion and a protonated dipolar phosphoramide which is rapidly deprotonated by the relatively basic 4-nitrophenoxide: ArOPO₃H^? + CH(CH₂CH₂)₃N(acetonitrile ? CH(CH₂CH₂)₃N⁺P(O)(OH)O^? + ArO^?? CH(CH₂ CH₂)₃N⁺PO₃^2?+ ArOH → CH(CH₂CH₂)₃N + PO₃^?. The postulated formation of PO₃^? by this route explains why the addition of quinuclidine to an acetonitrile solution containing the monoanion salt, ArOPO₃H^?R₄N⁺, and t?BuOH produces t-butyl phosphate at a faster rate than the addition of diisopropylethylamine to the same solution. 2,4-Dinitrophenyl phosphate, which was previously studied by the same techniques, reacts via oxyphosphorane intermediates from the diprotonated and the monoanion forms, and via monomeric metaphosphate, from the dianion form.     

Synthesis and characterization of cyclophane: The highly selective recognition of Fe3+ in aqueous solution and H2PO4− in acetonitrile solution

In this work, we report a series of cyclophane fluorescent sensors based on acridine combining with imidazolium through ether linkages. X-ray crystal structures demonstrated the self-assembly behavior of these cyclophanes in the solid state driven by hydrogen bond and π–π interactions. Sensors showed excellent selectivity towards Fe³⁺ in aqueous solution (H₂O/CH₃CN?=?49:1, v/v) and H₂PO₄^? in acetonitrile solution with notable color change under UV light, evident changes were also noticed in fluorescence spectra. In fluorescence emission, the obvious turn-off was induced by Fe³⁺ in aqueous solution and the obvious turn-on as well as bathochromic-shift was induced by H₂PO₄^? in acetonitrile solution.     

Structures of urea/thiourea 1,3-disubstituted thia[4]calixarenes and corresponding monofunctional receptors and their anion recognition properties

Two thiacalix[4]arenes in 1,3-alternate conformation functionalized by two (CH₂)₂NH(C=X)NHC₆H₄-NO₂-p groups (X = S,O) as well as two related monofunctional receptors MeO(CH₂)₂NH(C=X)NHC₆H₄-NO₂-p were prepared and characterized by X-ray crystal structures. The thioureido and ureido derivatives have E,Z and E,E conformations respectively both in monofunctional receptors and thiacalixarenes. The thiacalixarene attached thiourea groups are well separated from each other, but respective urea groups are much closer to each other and have mutual parallel orientation making the bisurea derivative a better preorganized receptor as compared to bisthiourea. Binding of Cl^?, F^?, H₂PO₄ ^? and AcO^? anions in chloroform and DMSO was studied by spectrophotometric and NMR titrations. In chloroform both bisurea and bisthiourea thiacalix[4]arenes bind anions 3–5 times stronger than corresponding monofunctional compounds in spite of better preorganization of the urea derivative. In DMSO simultaneous deprotonation of ureido NH groups of receptors and hydrogen bonding reactions are observed. Deprotonation by H₂PO₄ ^? is accompanied by a strong association between liberated H₃PO₄ and H₂PO₄ ^? (log K = 3.9). For hydrogen bonding associations the binding constants of H₂PO₄ ^? and AcO^? with bisurea thiacalixarene are up to two orders of magnitude larger than those with corresponding monofunctional receptor, but with bisthiourea thiacalixarene the effect is less than two-fold. Thus in this solvent in contrast to chloroform the preorganization is an important factor.     

α-Funktionelle 2-Methylphenylphosphane, 2-(HE?CH2)?C6H4?PH2 (E: O,NR, PH) I. Darstellung,Metallierungs- und Silylierungsverhalten

α-Functionalized 2-Methylphenyl Phosphines, 2-(HE? CH₂)? C₆H₄? PH₂ (E: O, NR, PH) I. Preparation, Deprotonation and Silylation Behaviour By reaction of different ortho-substituted phenyl phosphonates 2-X? C₆H₄? PO₃R₂ (X = COOR, CONHR, PO₃R₂) with LiAlH₄ α-functionalized 2-methylphenyl phosphines 2-(HE? CH₂)? C₆H₄? PH₂ (E: O, NPh, PH) are accessible. The title compounds are characterized by deprotonation and silylation experiments.     

Study on the equilibrium in the M(CH3COO)2 ? CH3OH ? H2O system (M  Mg2+, Ca2+, Ba2+) at 25°C

The complex formation and dehydration processes in the system M(CH₃COO)₂? CH₃OH? H₂O have been studied by the methods of the physico-chemical analysis at 25°C; (M = Mg²⁺, Ca²⁺ and Ba²⁺). In the Mg(CH₃COO)₂? CH₃OH? H₂O system. methanol was found to behave as a solvent in which complex formation reactions take place, including also methanolation of Mg²⁺. The fields of equilibrium existence of two new compounds have been found: Mg(CH₃COO)₂ · 3H₂O · CH₃OH and Mg(CH₃COO)₂ · 1,5 CH₃OH. In the systems M(CH₃COO)₂? CH₃OH? H₂O (M = Ca²⁺, Ba²⁺), methanol was found to react as a dehydrating reagent.     

Hydrothermal syntheses,crystal structures and thermal stability of two divalent metal phosphonates with a layered and a 3D structure

Two new divalent metal phosphonates, [Cu₂{CH₃C(OH)(PO₃)₂}(H₂O)₂]?·?0.5H₂O (1) and [NH₃CH₂CH₂NH₃][Zn₃{CH₃C(OH)(PO₃)₂}₂(H₂O)]?·?H₂O (2), have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction as well as with infrared spectroscopy, elemental analysis and thermogravimetric analysis. The structure of 1 comprises [Cu₃(hedp)₂]^2? layers connected by [CuO₄] units to form a 3D open-framework structure with a one-dimensional channel system along the b axis. In 2, the connections of alternately arranged [ZnO₄] tetrahedra, [ZnO₆] octahedra and [CPO₃] tetrahedra via vertex-sharing result in a 2D layered structure. The protonated ethylenediamine cations and water molecules are located between adjacent layers.     

Vibrational analysis of chlorinated methylphosphonic acid and its anions

The vibrational spectra (IR and Raman) of CH₂ClPO₃H₂ and of its anions in solutions of H₂O and D₂O are reported. The IR spectra of the solid dibasic sodium and potassium salts, the solid normal and O-deuterated monobasic sodium and potassium salts and of the solid normal and O-deuterated acid are discussed. Symmetry and internal stretching force constants, stretch-stretch interactions and potential energy distributions are obtained from normal coordinate analysis of CH₂C1PO₃H₂, CH₂ClPO₃H^? and CH₂C1PO₃^2?, and the calculated and observed frequencies for O-deuterated acid and monobasic anion are compared.     

Complexes of cadmium with phosphoric acid

We have investigated the behaviour of¹⁰⁹Cd, in two-phase systems: (HDEHP–C₆ H₆/ H₃ PO₄–HClO₄–LiOH, =0.2), as a function of the independent equilibrium parameters which define the system: pH, equilibrium concentration of H₃ PO₄ and total concentration of HDEHP in the organic phase. The data have been interpreted in terms of the existence of phosphoric complexes characterized by their order 1 with regard to H₃ PO₄ and their charge z. The l and z. values are: 0<1<2, z=–2, 0, 1, 2 for the following ranges: 0.7<pH<2.7 and CH₃ PO₄<4M. Stability constants of the predominant complexes have been obtained. Finally, a formulation of these complexes has been proposed on the basis of partial charge of the atoms. Some complexes, could be formulated as hydroxy-phosphoric species, resulting from competition between hydroxy and dihydrogenophosphate anions. In concentrated phosphoric acid (CH₃ PO₄=4M), complexation of cadmium is not more than 25%.     

Ionic strength and buffer capacity of wide-range buffers for polarography

A procedure for the calculation of the ionic strength and buffer capacity of a series of buffers prepared by the partial neutralization of a mixture of mono- and polybasic acids is outlined and data tabulated for a mixture 0.02 M in each of CH₃COOH, H₃PO₄, and H₃BO₃. The useful polarographic range of each buffer solution is also given. Illustrative calculations have also been made to show that, at any given pH value, the minimum buffer capacity required for polarographic reduction of up to 1 × 10⁻³ M solutions of an organic compound, and which involves hydrogen ions, is 0.006.     

Microdetermination of Molybdenum in Iron and Biological Samples by Adsorption Voltammetry

Abstract

Molybdenum has been determined by adsorption′voltammetry in a pH 2.40 buffer solution (0.005M N_aH₂PO₄-0.01M H₃PO₄). Utilizing the Strong adsorption of 12-molybdenum phosphate at a hanging mercury electrode, nanomole sensitivities are achieved. The derivative peak current is directly proportional to the concentration of molybdenum (VI) over the range of 5×10–9?2×10^?7M. The detection limit is 4×10^?9M.     

A 1,3‐Capped Calix[4] Conjugate Possessing an Amine Moiety as an Anion Receptor: Reversible Anion Sensing Detected by Spectroscopy and Characterization of the Supramolecular Features by Microscopy

A phenylenediamine‐capped conjugate of calix[4]arene ( L_amino ) was synthesized by reducing its precursor, L_imino , with sodium borohydride in methanol. The L_amino sample binds to anions due to the more flexible and bent conformation of the capped aminophenolic binding core, compared to the precursor L_imino . The L_amino sample showed selectivity towards H₂PO₄^? by exhibiting a ratiometric increase in emission by about 11‐fold with a detection limit of (1.2±0.2) μm ((116±20) ppb) over 15 anions studied, including other phosphates, such as P₂O₇^4?, adenosine monophosphate (AMP^2?), adenosine diphosphate (ADP^2?), and adenosine triphosphate (ATP^2?). The L_amino sample shows an increase in the absorbance at λ=315 nm in the presence of H₂PO₄^?, CO₃^2?, HCO₃^?, CH₃CO₂^?, and F^?. The ¹H NMR spectroscopic titration of L_amino with H₂PO₄^?, F^?, and CH₃CO₂^? showed major changes in the phenylene‐capped and salicyl moieties, and thereby, confirming the aminophenolic region as the binding core. However, the binding strength of these anions followed the trend H₂PO₄^?>F^??CH₃CO₂^?>HSO₄^?. The heat changes observed by isothermal titration calorimetry support this trend. The L_amino sample showed reversible sensing towards H₂PO₄^? and F^? in the presence of Mg²⁺ and Ca²⁺, respectively. NOESY studies of L_amino , in comparison with its anionic complexes, revealed that major conformational changes occurred in the capping region to facilitate the binding of anion. ESI‐MS and the Job's method revealed 1:1 stoichiometry between L_amino and H₂PO₄^? or F^?. In the SEM micrographs of L_amino , the spherical particles are converted into spherical aggregates and further form large agglomerates and even branched sheets in the presence of anions, depending upon their binding strength.     

New media in homogeneous catalysis: wet sodium or tetrabutylammonium hydrogensulfate salts for reppe syntheses catalyzed by a ru(ii) carbonyl complex

The ruthenium(II) complex fac-[Ru(CO)₂(H₂O)₃(C(O)C₂H₅)][CF₃SO₃] dissolved in aqueous tetrabutylammonium hydrogensulfate ([(CH₃(CH₂)₃)₄N][HSO₄]) or sodium hydrogensulfate (NaHSO₄) catalyzes the hydrocarboxylation of ethylene to propionic acid and additionally produces minor amounts of hydrocarbonylation products (diethyl ketone and propanal), under water-gas shift reaction conditions. This system is stable with a selectivity of 90% to propionic acid for high ethylene conversion. A turnover frequency of propionic acid, TOF(C₂H₅CO₂H)/24?h?=?5?×?10³ (TOF (C₂H₅CO₂H)?=?([(moles of C₂H₅CO₂H)/(moles of Ru)?×?rt)]?×?24?h) was achieved for Ru?=?7.45?×?10^?4?mol, [(CH₃(CH₂)₃)₄N][HSO₄]?=?80?g (2.36?×?10^?2?mol); H₂O?=?40?g (2.22?mol); CO?=?C₂H₄?=?20?g (total pressure?=?88?atm); T?=?150°C by a reaction time (rt) of 2.87?h. The countercation (sodium or tetrabutylammonium), the ruthenium concentration and the hydrogensulfate/H₂O ratio of the medium affect the catalytic reaction. A nonlinear dependence on total ruthenium concentration was shown. The data are discussed in terms of a potential catalytic cycle. Formation of propionic acid comes from hydrolysis, and formation of diethyl ketone and propanal comes from hydrogenolysis of the Ru-ketyl and Ru-acyl complexes, respectively.     

The unimolecular chemistry of [1,2-propanediol]+˙: a rationale in terms of hydrogen-bridged radical cations

By combining results from a variety of mass spectrometric techniques (metastatle ion, collisional activation, collision-induced dissociative ionization, neutralization–reionization spectrometry and appearance energy measurements) and the classical method of isotopic labelling, a unified mechanism is proposed for the complex unimolecular chemistry of ionized 1,2-propanediol. The key intermediates involved are the stable hydrogen-bridged radical cations [CH₂?C(H)? H…?O…?O(H)CH₃]⁺˙, which were generated independently from [4-methoxy, 1-butanol]⁺˙ (loss of C₂H₄) and [1-methoxyglycerol]⁺˙ (loss of CH₂O), [CH₃? C?O…?H…?O(H)CH₃]⁺˙ and the related ion-dipole complex [CH₂?C(OH)CH₃/H₂O]⁺˙. The latter species serves as the precursor for the loss of CH³˙ and in this reaction the same non-ergodic behaviour is observed as in the loss of CH³˙ from the ionized enol of acetone.     

Structure and formation of gaseous [C4H6O]+˙ ions: 1—The enolic ions [CH2C(OH)?CHCH2]+˙ and [CH2CH?CHCH(OH)]+˙ and their relationship with their keto counterparts

The [C₄H₆O]^+˙ ion of structure [CH₂?CHCH?CHOH]^+˙ (a) is generated by loss of C₄H₈ from ionized 6,6-dimethyl-2-cyclohexen-1-ol. The heat of formation ΔH_f of [CH₂?CHCH?CHOH]^+˙ was estimated to be 736 kJ mol^?1. The isomeric ion [CH₂?C(OH)CH?CH₂]^+˙ (b) was shown to have ΔH_f, ? 761 kJ mol^?1, 54 kJ mol^?1 less than that of its keto analogue [CH₃COCH?CH₂]^+˙. Ion [CH₂?C(OH)CH?CH₂]^+˙ may be generated by loss of C₂H₄ from ionized hex-1-en-3-one or by loss of C₄H₈ from ionized 4,4-dimethyl-2-cyclohexen-1-ol. The [C₄H₆O]^+˙ ion generated by loss of C₂H₄ from ionized 2-cyclohexen-1-ol was shown to consist of a mixture of the above enol ions by comparing the metastable ion and collisional activation mass spectra of [CH₂?CHCH?CHOH]^+˙ and [CH₂?C(OH)CH?CH₂]^+˙ ions with that of the above daughter ion. It is further concluded that prior to their major fragmentations by loss of CH₃˙ and CO, [CH₂?CHCH?CHOH]⁺˙ and [CH₂?C(OH)CH?CH₂]^+˙ do not rearrange to their keto counterparts. The metastable ion and collisional activation characteristics of the isomeric allenic [C₄H₆O]^+˙ ion [CH₂?C?CHCH₂OH]^+˙ are also reported.     

Determination of some elements in Ageratum conyziodes,a tropical medicinal plant, using instrumental neutron activation analysis

1-Hydroxy-2-ethylthioethane, CH₃CH₂SCH₂CH₂OH, (HETE) gave relatively stable intermediate sulfonium cations, with water solutions of mineral acids, which could be extracted into chloroform as ionic associates in the presence of bis(1,2-dicarbollyl)cobaltate anions labeled with ⁶⁰Co independently of the nature of the inorganic anion but depending on the activity of hydrogen ions. The water phase contained buffers and acids HCl, H₂SO₄, H₃PO₄ and HClO₄. The kinetics and mechanism of the reactions have been studied. This revised version was published online in August 2006 with corrections to the Cover Date.     

Comparative Study of Hypophosphite H2PO2^- Adsorption on Ni（111） and Ag（111） Surfaces by DFT

Surface structures and electronic properties of hypophosphite H2PO2^- on Ni（111） and Ag（111） surfaces were investigated by means of density functional theory at B3LYP/6-31 ＋ ＋G（d,p） level. The most stable structure was that in which the H2PO2^- adsorbs with its two P--O bonds faced to the substrate surface. The results of the Mulliken population analysis showed that because of the subtle difference of electron configuration, the adsorption energy was larger on the Ni surface than on the Ag surface, and the amounts of both donation and back donation were larger on the Ni（111） surface than on the Ag（111） surface. There were more negative Mulliken charge transfer from H2PO2^- to substrate clusters on Ni surface than on Ag surface and more positive Mulliken charges on P atom in Ni4H2PO2^- than in Ag4H2PO2^-, which means that P atom in Ni4H2PO2^- is easily attacked by a nucleophile such as OH . Thus, H2PO2^- is more easily oxidated on Ni（111） surface than on Ag（111） suface. These results indicated that the silver surface is inactive for the oxidation reaction of the hypophosphite anion.